Next time, try Permatex gasket sealant on bolts. It is a gummy liquid, perhaps butyl rubber like the adhesive used on modern windshields, but it stays pliable. It is very sticky, but cleans up easy with ethanol. I keep a small can on the shop table since I use it so much and the can lasts for years without hardening. Has a brush-in-lid like PCV solvent. You can also coat gaskets with it, which is it's main purpose, but not too much or the gasket can squish out. I haven't tried gasket shellac, which I think sets up harder. For things like weatherstrip rubber repair and sealing cracks from rainwater, I like polyurethane caulk. It is better than silicone caulk.
